1. Field of the Invention
Embodiments of the present invention relate to a secondary battery.
2. Description of the Related Art
A secondary battery is reusable because it can be charged and recharged. Due to its reusability, the secondary battery may be employed as a power source for a computer (e.g., a notebook computer or a laptop computer), a portable communication device (e.g., a mobile phone and a camcorder), etc.
Electric vehicles have been under development to reduce the environmental pollution due to exhaust gas from vehicles utilizing internal combustion engines. In order to apply the secondary battery to an electric vehicle, the development of an economical, high-speed chargeable, stable, and high-energy capacity secondary battery is desired.
A secondary battery can often be classified as either a lead battery, a nickel/cadmium (Ni/Cd) battery, a nickel/metal hydride (Ni/MH) battery or a lithium ion battery according to its negative electrode material and/or positive electrode material. Potential and energy density of the secondary battery is determined by properties of the electrode material. The lithium ion battery with its lithium electrode material can be used as a power source for a portable electronic device and for an electric vehicle because the energy density of lithium is relatively high due to a low redox potential and low molecular weight.
However, when the secondary battery is incorporated into a product, it is exposed to external impacts during use. Accordingly, a secondary battery having improved stability under external impacts is needed.